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@Dammit
We're slowly closing in on the engine specification, it's been evolving over time but I think we've got some conclusions on some parts now.
The M96 engine is slightly odd in that the crank, at the flywheel end, is unsupported - which had consequences.
Initially the crank was solid, which meant that as it flexed it transferred significant load into the closest main bearings, dramatically increasing the wear on those. Porsche decided to make the next generation of cranks hollow at the end - and machined out the centre. This made the crank more flexible, but the flex was contained within the hollow part of the crank, not transmitted straight into the bearings - but these cranks can crack.
So we're returning to a solid crank - forged from EN40B steel. We're also fitting an additional bearing that sits right behind the RMS, which requires said seal to stand slightly further out than stock. The only EN40B cranks available are for the 3.6 litre engines (when bore is 96mm) rather than the 3.4 which I currently have.
I'm in the process of sourcing a 3.6 litre crank carrier - the main bearings are usefully thicker than the 3.4 as well, so this is all good news. We'll use Carillo rods, and new pistons to fit into the 100mm Capricorn liners which will be fitted after the stock liners are machined out. We'll close the deck at this point, also. This will give us a swept capacity of 3.9 litres, so up 0.5 litres from my current engine.
The heads are being lightly ported, the tappet chests we are completely redesigning and will have machined from billet in order to address some issues that they suffer from as stock, and also allow for higher lift cams to be fitted - these will be specified and ground to match the new capacity and overall design of the engines. I believe we're sticking with stock valves as they flow (impressively) well.
Porsche motorsport provide the X51 kit for the 3.4 engine, and we're using some of their parts here - specifically the intake manifold, the extra oil scavenge pump fitted to one head and the additional radiator that fits beneath the number plate - with an additional thermostat inline to stop it opening too early.
Exhaust manifolds are likely to be Cargraphic long-tube, equal length items as they are the correct diameter for our predicted use.
Not sure on the throttle body at the moment, an 82mm unit of some description but I don't know which one, I'd prefer to stick with cable, but the Syvecs unit can support eGas and that might be easier.
With the new crank, ARP fasteners, Carillo rods and the revised tappet chest we should be ok to push the rev ceiling on the engine up a little, will be very interesting to see what the engine designer thinks is appropriate there - the 3.7 is over-square, the 3.9 has a longer stroke so is not as suited to a high revving application, but that said the engine is going to be pretty robust with the updates so we shall see.